C i.e. Anencephaly Neural tube defects (NTDs) i.e. anencephaly, meningomyelocele, encephalocele and spina bifidaQ can be caused by antifolate & antiepileptic drugs, maternal diabetes, lower maternal folate status, reduced activity of 5, 10, methylene - THE reductase (MTHFR) enzyme (d/t C677 T-polymorphism in MTHFR gene) and possibly by mutation of other enzymes eg. methionine synthase and serine-glycine hydroxymethylase. Folate supplementation at the time of conception and in first 12 weeks of pregnancy reduce 70% incidence of NTDs (and also hare lip and cleft palate). - Neural tube defects are best detected by amniocentesisQ. Earliest detectable congenital anomaly on USG is anencephalyQ. It can be diagnosed as early as at 10 weeksQ. It is best diagnosed (100% accuracy) at 12 week.Q - Karyotypic analysis (for chromosomal abnormalities), biochemical & molecular analysis of DNA obtained from cells can be done in either chronic villi of 1,, trimester or amniotic fluid of 2nd fetus. Test Done at Comment Amniocentesis 14-16 weeksQ - M.C. used procedure; M.C. reason to perform this is advanced maternal age (removal of small (early 2nd (>35 yrs), the best known correlate of trisomy amount of amniotic trimester) - Other reasons are ? fluid) 1. Abnormal (maternal serum) triple marker assayQ (HCGQ, a-FetoproteinQ and unconjugated estriolQ in maternalQ serum) and inhibin also (in quad marker assay) predict risk of trisomy 21 or 18 2. Mid trimester USG abnormalitiesQ - estimated risk of chromosomal abnormality is dependent on USG finding & is maximum in cystic hygromaQ >Omphalocele > congenital hea ds > nonspecific > choroid plexus cyst 3. More recently, 1, trimester screening involving measurement of nuchal translucency (on USG) and levels of PAAP-A and HCG are used to identify women at increased risk. Early Amniocentesis 12-14 weeks Has greater risk of spontaneous aboion or fetal injury but provides results at an earlier stage of pregnancy Chrionic Villus Earlier (8-12 - 2nd m.c. procedure. It allows for an earlier detectionQ of abnormalities & a safer Sampleing (CVS) wks)Q pregnancy termination (d/t early diagnosis), if desired (Transcervical/ preferably 10-12 - Spontaneous aboions are more common in comparison to amniocentesis but is abdominal biopsy of wks. overall a safe procedure (spontaneous aboions fetal trophoblastic - Risk of limb defectsQ increases if CVS is doneweeks.So it is applicable tissue/chorion) during very narrow window of time Percutaneous 2nd -- 3.1 trimester - Done under USG control. Usually performed when USG abnormalities are Umbilical Blood of pregnancy detected late in 2,,d trimester. Sampling (PUBS) (> 18 wks) - Also done to clarify cytogenetic results of amniocentesis as detection of (fetal blood for lvmphocvtic culture) mosaicism. Pre implantation Before implant- To detect single gene disorder such as -Mn : "SC ST" molecular diagnostic ation invitro S - Sickle Cell Anemia testing (eg- PCR) feilizationQ at C - Cystic fibrosis 8-10 cell stage ST - Sachs-Tay disease (Tay-Sachs ds) * Endometrial biopsy is done at Premenstrual periodQ to avoid risk of endometriosis. Chordocentesis is done at 18 wee Q. Amniocentesis is not useful in cleft lip detection. Golden Amniotic fluid is diagnostic of Rh incompatibilityQ. Saffron coloured meconium is seen in post maturityQ.